Conventionally, methods are known that convert an image of an object (object image) formed on an imaging device plane by using the imaging device that utilizes photoelectric transducers, such as CCDs (charge coupled devices) and CMOSs (complementary metal-oxide semiconductors), and that thereby record the image.
With advancements in microprocessing technology, there have been implemented, for example, processing rate enhancements of central processing units (CPUs) and higher level integration of storage mediums, thereby enabling high speed processing of a large volume of image data that have not been able to be handled before. In addition, also for photoreceptor devices, enhancements in high-level integration, compactness, and the like have been implemented, in which the high-level integration has enabled even higher spatial frequency recording, and the compactness has enabled overall camera compactness.
Further, so as to be able to be used in wide range photographic conditions, the demand for zoom lenses has been increased, and more specifically, the demand has been increased for high zoom ratios.
However, in an optical system with a high zoom ratio, since the angle of viewing is narrowed in a telephoto end mode, even a small motion blur causes the occurrence of a large blur in the image. As such, especially for video cameras with high zoom ratios, so-called electronic motion blur compensation systems are known that cause shifting of an image capture range of the photoreceptor device in order to compensate for the motion blur.
In addition, conventionally, so-called motion blur compensation optical systems are known that cause shifting of some lens groups constituting a lens system in the substantially vertical direction with respect to the optical axis, thereby to compensate for optical performance deterioration in the event of shifting of the image position.
In a motion blur compensation optical system of the above-described type, the function of an optical motion blur compensation system can be obtained from the combination of a detection system for detecting such image blur caused by camera shaking that occurs in association with motion blur caused with shutter releasing operation, a control system for imparting a compensation amount to the lens position in accordance with a signal detected from the detection system, and a drive system that causes shifting of a predetermined lens in accordance with an output from the control system.
According to the optical motion blur compensation system, an image can be shifted in accordance with lens shift performed by the drive system, such that the blur associated with the blur in the camera can be compensated for in accordance with the lens shift performed by the drive system.
Motion blur compensation optical systems of the above-described type are known as disclosed in for example, Japanese Patent Laid-open Publications No. 2002-244037, No. 2003-228001, and No. 2003-295057.
According to a zoom lens disclosed in Japanese Patent Laid-open Publication No. 2002-244037, a third lens group disposed on the image side of an aperture diaphragm is configured to include a negative sub lens group, in which the image is shifted by shifting the positive sub lens group.
According to a zoom lens disclosed in Japanese Patent Laid-open Publication No. 2003-228001, a third lens group disposed on the image side of an aperture diaphragm is configured to include a negative sub lens group, in which the image is shifted by shifting the positive sub lens group.
According to a zoom lens disclosed in Japanese Patent Laid-open Publication No. 2003-295057, the image is shifted by shifting the entirety of a third lens group.
In the conventional motion blur compensation optical systems, the lens group disposed near the aperture diaphragm is shifted, such that interferences tend to occur among a drive mechanism of causing the shifting, a mechanism of opening and closing the aperture diaphragm, and a mechanism of moving the respective lens in the event of, for example, zooming or focusing, so that a lens barrel has to be enlarged in the radial direction.
An object of the present invention is to solve the problems described above, thereby to provide a zoom lens and an imaging apparatus using the zoom lens, the zoom lens being suited for achieving compactness without increasing the number of lenses and being capable of implementing motion blur compensation.